Spark plug



July 28, 1925.

w. R. YARLo-r-r SPARK PLUG F1ed No v. 16, 1923 Patented `luly 28, 1925.

UNITED STATES WILLIAM RAY YARLoT'r, or nnrnorr, MICHIGAN.

SPARK PLUG.

Application led November 16, 1,923. Serial No. 675,175.

To all 'whom it may concern.:

-Be it known that I, WILLIAM RAY YAR- i Lorr, a citizen of theUnited States, residing at Detroit, in the county of Wayne and State of Michigan, have inventedl new and useful Improvements in Spark Plugs, of

which the ,following is a specification.

The present invention relates to improvements in spark plugs for use with internal combustion engines, and has, as its object,

to provide a construction adapted to prevent the formation of carbon and oil deford a comparatively Asimple and durabh construction, particularly in the means for eliminating checking or cracking of the porcelain, which ordinarily surrounds the central electrode, thus-eliminating leakage of current through the wall of the core to the metallic shell.

A further object of the invention is tov afford a comparatively simple and vvery durable construction, particularly in the means for securing in position the ground electrode which is ordinarily directly soldered or secured to the shell.

The above and other objects of the invention are obtained by providing a spark plug comprising, broadly, a metallic shell serving to receive a core or tube of porcelain or other linsulating material .which encloses an electrode. The shell is provided with a lining ofa suitable heat retaining and ielding insulating material, such as mica.

` his lining is preferably built up from a series of layers of material, such as mica rings, and is constructed to form a seat for the porcelain tube. The spark plug includes a core or tube, preferably of porcelain, having a shoulder which abuts the end of the lining, the latter preventing movement of the tube longitudinally of the shell in one direction. The lining extends preferably not less than an inch and a half through the` shell, and being spaced from the porcelain tube or core, provides not only seating means for the core, but, by reason of its retention of heat, serves to prevent the deposite of carbon andV oil upon the core. Moreover, the mica lining, by reason of its retention of heat, prevents rapid coollng of the porcelain core, which tends to check or crack the same.

The entire tube is insulated from the shell by means of a lining additional to the one mentioned above, and positioned between the shell and the portion of the tube provided with the shoulder.

In the accompanying drawings, there is illustrated, ,for the purpose of making the -invention clear, one embodiment of the same, and in these drawings:

Fig. l1, is an elevational view.

Fig. 2 is a longitudinal sectional view.

Fig. 3 is a transverse section on the line 3-d3, looking in the direction of the arrows, an

Fig. 4 is a plan view of the ground electrode.

Referring to the drawings for a more detailed description, 1() indicates a shell having a shank portion 11 which is threaded, as is usual. lAn insulating tube or core 12, preferably of porcelain, extends axially of the shell, and has an intermediate portion 13 of enlarged diameter to form an under shoulder `14 and an upper shoulder 15. The core is 'spaced from the wall of the shell, and is insulated therefrom by means of a lining of suitable yielding and heat retaining insulating material 16 which is preferably built up from a series of-superposed rings. Mica is the 'preferred material, since it retains the heat and readily yields. Furthermore, the. construction of the lining from a number of. layers or rings of mica improves its yielding qualities. The lower end of the lining is positioned above an inturned flange 17 upon which rests the ground electrode 18. The electrode has a body portion/1 9, in the form of a split ring, which seats upon the flange and is provided with a terminal portion 20 extending through an opening 21 in the flange. The annular portion of the electrode is flattened, as indicated in Figure 2, and the lining 16 rests thereon. It will be noted that the lining of mica terminates at the shoulder 14, the shoulder resting against the end of the lining which prevents movement of the core longitudinally of the shell 'in one direction. The l,enlarged intermediate portion of the core may be insulated from the shell byfmea'ns of a continuation of the lining in the form of a wrapping 22 of inlio sulating mater-iai, such as mica, and an inturned flange 23 at the upper end of the shell vserves to compress a, gasket 24 to hold the core against upward movement within the shell.- It will be, of course, understood that-this continuation of the lining in the form of the wrapping 22 is not a necessary Ifeature of the invention, since the porcelain4 burn the carbon and oil deposits as well as prevent the rap-id cooling' of the porcelain core, which has a tendency to check or crack when cooled too rapidly.

It should be observed that the shank of the shell and the lining are of substantial length; preferably the lining extends through the vshell for not less than an inch and a half, so that a very considerable firing space is provided, and the distance to be traversed in order to short Acircuit the spark is approximately six inches.

The mica lining forms a comparatively I yielding seat for the rather frangible porcelain core Which is a substantial improvement'over the unyielding metallic shoulder which is usually provided upon the interior of the shell to serve as a seat for the core. The construction of the lining from a series of layers or superposed mica rings tendsto make the seat for they porcelain core more yielding than would be the case were the lining formed from a single piece of mica or similarv material. i

In addition to the external insulation, or internal insulating lining of mica within the core is provided. It will be observed that the upper portion oi the bore is enlarged as' at 26` and around the electrode 25` are insulating disks 28 of mica forming a shell which extends from substantially the end of the liningl to above the upper end yof the shell. By reason of this insulation,

should the porcelain crack around the flange 23 the shell will not short circuit the plug. The end of the electrode 25 fits within a connector plug 29 threaded into the upper end of the core.

It should'be understood that such modiiications may be made in the structure illustrated and described as' come within the scope of the following claims.

I claim:

1. In `a spark plug, a metallic shell, an

' insulating `tube extending axially through said shell, an electrode within the tube extending longitudinally thereof, the tube being formed with a shoulder intermediate its ends, and an insulating lining of mica within said shell fitting closely against'the wall Iof the shell and surrounding and spaced from the portion of said tube at one side of the shQulder, said'lining forming a seat for said shoulder and serving'wholly to hold the tube against movement longitudinally of the shell in one direction.

2. In a spark plug, a metallic shell, an insulating tube of porcelain extending axially through said shell, an electrode within the tube extending longitudinally thereof, the tube being formed with a shoulder intermediate its ends, an insulating lining of mica within said shell fitting closely against the wall of the shell and surrounding and spaced from the portion of said tube at one side of the shoulder, said lining forming a seat for said shoulder and serving wholly to hold the tube against movement longitudinally 0f the shell in one direction.

3 .In a spark plug, a metallic shell, an insulating tube extending axially through said shell, an electrode within the tube extending longitudinally thereof, the tube being formed witha shoulder intermediate its ends, an insulating lining of mica Within said shell'tting closely against the wall of the shell and surrounding and spaced from the portion of said tube at one side of the shoulder, said lining formi-ng a seat for said shoulder and serving wholly to hold the tube against movement longitudinally of the shell in one direction, an inturned flange at one end of said shell serving to support said lining, and a ground electrode having a substantially annular portion supported on said flange between the same and said lining.

4. In a spark plug, an insulating tube of` frangible material extending axially through said shell, an electrode within the tube extending longitudinally thereof, the tube being formed with a shoulder intermediate its ends, an insulating lining of mica within said shell surrounding and spaced from the portion of said tube at one side of the shoulder, said lining forming a l seat for said shoulder andv serving wholly to hold the tube against longitudinal movenient of the shell in one direction, and an interior lining of insulating material within the tube between the same and said elecins trode, said interior lining extending from .120

built up from a series of superposed layers and being formed to afford a seat for said shoulder adapted to hold the tube against movement longitudinally of the shell in one direction, said lining supporting the tube out of contact with the shell. v

6. In a spark plug, a metallic shell, an insulating tube of porcelain extending axially through said shell, an velectrode within said tube, said tube being formed with a shoulder intermediate its ends, an insulating lining ofvmica within said shell, said lining being built up from a series of superposed layers and being formed to afford a seatA for said shoulder adapted to hold the tube against movementlongitudinally of the shell in one direction, said lining supporting the tube out of Contact with the shell.

7. In a spark plug, a metallic shell, a porcelain insulating tube extending axially through said shell, an electrode extending through said tube, the tube having an intermediate portion of enlarged diameter to form upper and lower shoulders, means at one end of the shell for holding the tube against longitudinal movement in One di- `rection, an insulating lining of mica within the shell around the tube and spaced from the tube, said lining extending from one end of the shell to the lower shoulder of said tube and engaging said shoulder to hold the vtube against movement in thel other direcaround the \tube and spaced from the tube to said lower shoulder, the lining forming a seat at said lower shoulder, and the shoulder abutting said seat whereby the tube is held against movement in the other direction longitudinally of the shell, said lining serving to supportthe tube out of contact with said shell,l an electrode extendin throu h said tube, and a-secondelectro e at t e Y lower end of the shell.

tube being formed with a shoulder intermediate its ends, an insulating lining of mica within said shell surrounding and spaced from the portion of said tube at one side of the shoulder, said lining yforming a seat for said shoulder and serving wholly to hold the tube against longitudinal movement of the shell in one direction, and an interior lining of insulating material within the tube between the same and said electrode, said interior lining extending from substantially the upper end of said lining past the end of the shell above said shoulder;

10. In a spark plug, a metallic shell, an insulating tube of frangible material extending axially through said snell, an electrode within the tube extendino' longitudinally thereof, the' tube being fbrmed with the shoulder intermediate its ends, an insulating lining of mica within said shell extending substantially throughout the entire length thereof, said lining being formed intermediate its ends with a shoulder forming a seat for said tube shouldei` and below the tube shoulder serving t0 surround the portion of said tube and being spaced from said portion of the tube, said V)linin serving Wholly tosupport and hold the tu e against movement longitudinally of the shell in one direction, yand an interior lining of insulating material within said tube between the same and the electrode extending from the upper end of said lining past the adjacent end of the shell.

11. In a spark plug, a metallic shell, a porcelain insulating tube extending axially through said shell, an electrode within the tube, a lining of yielding heat retaining insulating material Within the shell and ex- 100 tending substantially throuvhout the length thereof, said lining completely insulating said electrode from the shell.

12. In a spark plug, a metallic shell, a porcelain insulating tube extending axially 105 through said shell, an electrode within the tube, a lining of yielding heat retaining insulating material within the shell, said lin- 'ing serving whollyr to support the tube out v out of contact with the shell againstmovement longitudinally of the shell inone di'- rection. l.

In testimony whereof I have hereunto set my hand.

, WILLIAM RAY YARLOTT. 

